Colorless crookes glass



COLOBLESS cnooxns GLASS.

No Drawing.

This invention relates to an improvement of the well known Crookes glass which has heretofore been largely used in making spectacle lenses. The important property of this glass resides in its efficiency to absorb or retard the ultra-violet rays and thus prevent these rays from irritating the eyes of spectacle users, withoutappreciabl Y reducing the transmission of visible ligit. The ingredients used to eliminate the objectionable rays have heretofore slightly colored the glass. It is well known, for example, that cerium is one of the most etlicientingredients of the Crookes glass to absorb these objectionable rays, but a pu e cerium Crookes g'lass is of a yellow tint and this tint' renders the glass objectionable.

Cerium for several reasons is probably the most convenient element to use in producing Crookes glass and it is the object of our invention to obviate the yellow tint that is characteristic of cerium while at the same time maintainin the efficiency of the glass to absorb the ObJGCtlOllfilJlG ultra-violet rays. We have found that didymium while havmg the property in itself-ofiabsorbing the ultra-violet rays will also neutralize the yellow tint given to the glass by cerium, and when properly added to the glass in correct pro ortions with the cerium will neutralize tie yellow tint imparted to the glass by the cerium and atlhe same time, together with the cerium will efficiently absorb the ultra-violet rays and thus produce a racticallycolorless Crookes glass.

.he didymium has ultra-violet ray absorptive properties practically equal to that of cerium and in consequence the amount of cerium, and, therefore, of the yellow color, can be reduced to such an extent that the total content of cerium and didymium will. give to the glass the required ultra-violet my absorptive properties and at the same time the didymlum will neutralize the coloring effect of the cerium in the glass and plroduce apractically colorless Crookes g ass.

The other ingredlents of the glass may be "0mm STATE-s Application filed May 11, 1925. Serial No. 29,618. )5; i

PATENT: orries,

PHILIP vrc'ron WZLLINGHAM GELL, CHARLES EDWIN: GOULD, WILFBED auras:

mirrro AND HAROLDSHARPE MARTIN, on smn'rnwrcx, ENGLAND, ASSIGNOBS TO omen anornnns AND 00., LIMITED, on smnrnwrc'x, ENGLAND.

those in common use and the process of making the glass is that commonly employed. The proportion of cerium in the glass mix may vary somewhat above or below 3.3% and that of the didymium somewhat above or below 0.7%.

\Ve do not, however, intend by specifying the use of cerium and didymium to limit.

our invention to the use of those two elements. Other elements known to the skilled glass maker have the property of absorbing ultra-violet rays such as titanium, vanadium,

erbium, etc, but they are more expensive than cerium and as far as we know, they have never before been combined in such proportions as to produce the double effect.

of eliminatin the objectionable rays wh le neutralizing their individual coloring efiects and as far as we are aware we are the first to make use of two elements both of which 7 will retard the ultra-violet and of which one will neutralize the color imparted to the glass by the other. By the use of two or more of such elements the quantity-of each entering the glass batch may be reduced, and therefore, its coloring of the glass batch is correspondingly reduced and,

furthermore, they may be mixed in such roportions that the coloring of one will be neutralized by that of the other. 7

By our invention, therefore, we have produced a glass highly etlicient in absorbing or retarding the ultra-violet rays and at the same time we have produced a colorless glass containing cerium in suflicient quantities to A partially absorb the ultra-violet rays and (lidymium in suflicient quantities to assist in he absorption of 'such ra s and to neutralise the color that would we imparted to.

the glass by the cerium, and with the cerium to absorb practically all the ultra-viola 2. A glass for use in lenses, said glass I I containing approximately f ce ium o In ts tiniony whereof we havsigned Qilr partially absorb the ultra-violet rays and names to this specificatiomapproximately .7% of didymium to mist in the absorption of such rays and to neu- PHILIP 'wcToR WILUNGHAM' cm." 6 trahze the color that would be imparted to o CHARLES EDWIN GOULD. the glass by the cerium and with the cerium Will-RED MARSH HAMPTON.

to absorb practically all the ultra-violet rays. HAROLD SHARPE MART. 

